1. Field of the Invention
This invention relates to antibiotic combinations for topical use. Specifically, it relates to the synergistic combination of an aminoglycoside, a benzylpyrimidine, and a sulfonamide.
2. Description of the Prior Art
Aminoglycosides are antibiotics which inhibit bacterial protein syntheses. Sulfonamides competively inhibit the utilization of paraamino-benzoic acid by bacteria which synthesize folic acid. Benzylpyrimidine like trimethoprim, also interfere in the synthesis bacterial folic acid at a stage just following the supposed interference by the sulfonamide. The advantages of the sequential involvement of sulfonamides and benzylpyrimidines in the interference of folic acid synthesis, purines and, ultimately, bacterial DNA have been exploited by their synergistic combination. Such combinations (e.g., co-trimoxazole =trimethoprim and sulfamethoxazole) are particularly useful in treating urinary tract infections. Combinations of trimethoprim and polypeptide antibiotics, such as polymyxin, or aminoglycosides, such as gentamicin, have been shown to be synergistic in vitro (Proc 10th Intl Congress Chemother. 438-439 [1978]). The combination of tobramycin with trimethoprim and sulfamethoxazole is also known an synergy has been alleged; however, such prior art combinations were limited to clinical evaluation of cancer patients' response on the separate intravenous administration of tobramycin and trimethoprim-sulfamethoxazole dosage (oral or intravenous) regimens (Rev. Inf. Disease 4 [4]:579-585 [1982]; Am. J. Med. Sci. 279 [1]:4-13 [1980] ). Some in vitro synergy against Serratia marcescens was demonstrated between co-trimoxazole and gentamicin (Proc 10th Intl Congress Chemother. 434-436[1978]). Beyond these experiences, there is nothing in the prior art which would suggest the topical combinations of the present invention or their precise concentration ranges which achieve true synergy of all components without creating or enhancing any antagonistic effects of any pair.